Convert remaining Danger rules to work locally

https://gitlab.com/gitlab-org/gitlab-ce/issues/66596 kicked things off, but it would be great to convert the remaining Danger rules to work locally:

• [ ] metadata - N/A
• [ ] roulette - N/A
• [ ] gitlab_ui_wg - N/A
• commit_messages - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/16593
• changelog
• specs
• single_codebase
• ce_ee_vue_templates
• only_documentation